From f10f4ac29ca360dd2507229d24e01502f0019c85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Patrick=20L=C3=BChne?= <patrick-github@luehne.de>
Date: Sun, 4 Sep 2016 14:49:34 +0200
Subject: [PATCH] Added back reference expressions to make the expression tree
 structure simpler.

---
 include/plasp/pddl/Expression.h            |  6 ++
 include/plasp/pddl/expressions/Reference.h | 75 ++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 include/plasp/pddl/expressions/Reference.h

diff --git a/include/plasp/pddl/Expression.h b/include/plasp/pddl/Expression.h
index cf5fb35..4b58dca 100644
--- a/include/plasp/pddl/Expression.h
+++ b/include/plasp/pddl/Expression.h
@@ -62,6 +62,11 @@ class PrimitiveType;
 using PrimitiveTypePointer = std::unique_ptr<PrimitiveType>;
 using PrimitiveTypes = std::vector<PrimitiveTypePointer>;
 
+template<class Type>
+class Reference;
+template<class Type>
+using ReferencePointer = std::unique_ptr<Reference<Type>>;
+
 class Unsupported;
 using UnsupportedPointer = std::unique_ptr<Unsupported>;
 
@@ -89,6 +94,7 @@ class Expression
 			PredicateDeclaration,
 			Predicate,
 			PrimitiveType,
+			Reference,
 			Unsupported,
 			Variable,
 		};
diff --git a/include/plasp/pddl/expressions/Reference.h b/include/plasp/pddl/expressions/Reference.h
new file mode 100644
index 0000000..b7ca69a
--- /dev/null
+++ b/include/plasp/pddl/expressions/Reference.h
@@ -0,0 +1,75 @@
+#ifndef __PLASP__PDDL__EXPRESSIONS__REFERENCE_H
+#define __PLASP__PDDL__EXPRESSIONS__REFERENCE_H
+
+#include <plasp/pddl/Expression.h>
+
+namespace plasp
+{
+namespace pddl
+{
+namespace expressions
+{
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+//
+// Reference
+//
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template<class Type>
+class Reference: public ExpressionCRTP<Reference<Type>>
+{
+	public:
+		static const Expression::Type ExpressionType = Expression::Type::Reference;
+
+	public:
+		Reference(Type *value);
+
+		Type *get();
+		const Type *get() const;
+
+		ExpressionPointer normalize();
+
+	protected:
+		Type *m_value = nullptr;
+};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template<class Type>
+Reference<Type>::Reference(Type *value)
+:	m_value{value}
+{
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template<class Type>
+Type *Reference<Type>::get()
+{
+	return m_value;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template<class Type>
+const Type *Reference<Type>::get() const
+{
+	return m_value;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+template<class Type>
+ExpressionPointer Reference<Type>::normalize()
+{
+	return nullptr;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+}
+}
+}
+
+#endif